Braking Distance Calculator

Written byOleh Soloninupdated 25 September 2026

Speed, km/h

Reaction time, s

The Russian Wikipedia calls 0.8 s typical within a spread of 0.4 to 1.5 s; the English one uses 1.5 s for accident reconstruction.

Surface

Gradient, % (downhill negative)

Result

Stopping distance, m70.5
Covered while reacting, m25
Braking itself, m45.5
The same 20 km/h faster, m98.5
In 4.5 m car lengths15.7
Surface and gripdry asphalt, grip 0.7
Range across the source64.8 to 70.5 m (grip 0.8–0.7)
Working
90 km/h = 25 m/s; reaction 25 × 1 = 25 m; braking 25² ÷ (2 × 9.81 × 0.7) = 45.5 m; total 25 + 45.5 = 70.5 m

Reaction plus braking

Works out the total stopping distance from speed, driver reaction time, the grip of the surface and the gradient of the road.

Stopping distance comes in two parts. While the driver reacts, the car carries on as before: 25 metres in a second at 90 km/h. Then braking begins, and its distance is the speed squared over twice the grip times gravitational acceleration.

The grip figures come from the Russian Wikipedia article on stopping distance (Остановочный путь): dry asphalt 0.7–0.8, wet 0.35–0.45, an icy road 0.1–0.2. The calculator works from the low end, which gives the longer distance, and shows the high end as the best case. The English Wikipedia's Braking distance article puts wet or frozen asphalt at 0.25 or lower, so a wet road can be worse than the low end. For snow, gravel or anything else, enter your own coefficient.

How to use

Enter the speed in km/h and the reaction time in seconds.
Choose a surface, or "Your own coefficient" and enter the grip.
On a downhill road, enter the gradient in percent as a negative number.
Read the stopping distance, its two parts, the range across the source and the distance 20 km/h faster.

Stopping distance by speed and surface

Each row is a separate run of the calculator with a one-second reaction, no gradient and the low end of the grip range. Reaction distance grows in step with speed; braking distance grows with its square.

Every row comes from the calculator on this page.
Speed	Surface	Reaction	Braking	Total
50 km/h	dry asphalt, 0.7	13.9 m	14 m	27.9 m
60 km/h	dry asphalt, 0.7	16.7 m	20.2 m	36.9 m
90 km/h	dry asphalt, 0.7	25 m	45.5 m	70.5 m
110 km/h	dry asphalt, 0.7	30.6 m	68 m	98.6 m
130 km/h	dry asphalt, 0.7	36.1 m	94.9 m	131 m
60 km/h	wet asphalt, 0.35	16.7 m	40.5 m	57.2 m
90 km/h	wet asphalt, 0.35	25 m	91 m	116 m
60 km/h	icy road, 0.1	16.7 m	141.6 m	158.3 m

What this calculator shows

The stopping distance split into reaction and braking
The spread across the source's range of grip
The same stop 20 km/h faster, and the distance in car lengths

What to keep in mind

Grip is constant over the whole braking distance and the brakes act at once — no brake response time is added.
The gradient in percent is applied as a correction to the grip; for road gradients this is close to the sine of the angle.
Car lengths assume a 4.5-metre car.

FAQs

What reaction time should I use?

The Russian Wikipedia gives 0.8 s as typical within 0.4 to 1.5 s; the English one uses 1.5 s for accident reconstruction. The default here is 1 s; at 1.5 s the stop from 90 km/h on dry asphalt grows from 70.5 to 83 m.

Why does braking distance grow faster than speed?

The brakes have to dissipate kinetic energy, which scales with the square of speed. From 60 km/h the braking part on dry asphalt is 20.2 m; from 90 km/h it is 45.5 m — half as fast again, 2.25 times the distance.

How much longer is it on a wet road?

At the low ends of the source's ranges, grip halves from 0.7 to 0.35, and the braking part doubles with it: 91 m instead of 45.5 from 90 km/h. The reaction distance stays at 25 m.

How do I work out a stop on snow?

Choose "Your own coefficient" and enter the grip: the source gives no figures for snow or gravel, and the calculator does not invent them. With 0.25 from 60 km/h you get 73.3 m.

How does a downhill gradient change it?

Going downhill, part of the grip is spent holding the car back. From 90 km/h on dry asphalt on an 8% descent the stop is 76.4 m instead of 70.5; on a steep icy descent the car will not stop at all, and the calculator says so.

How far does the car travel while I react?

The speed in metres per second times the reaction time. 90 km/h is 25 m/s, so each second of hesitation is 25 metres without braking.

Worked example

Ninety on dry asphalt

Input: 90 km/h, reaction 1 s, dry asphalt

Output: 70.5 m: 25 m reacting and 45.5 m braking

Note: At a grip of 0.8 it would be 64.8 m. On wet asphalt the same speed takes 116 m, and 110 km/h on dry takes 98.6 m.

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